The present invention relates to a knitting machine or the like with a device for raising and lowering the platen.
Knitting machines, particularly stocking -making machines, are known with devices for raising or lowering the platen. These devices comprise a system of levers which act on a frame which supports the platen above the needle-bearing cylinder and is associated with the supporting structure of the machine with the possibility of sliding along a direction which is parallel to the axis of the needle-bearing cylinder. The system of levers is connected to a cam-bearing cylinder which controls the various operations of the machine and intervenes on the levers, giving rise to the raising or lowering of the platen according to the requirements of the process in progress.
Usually, controlled raising or lowering are required during the formation of the edge of the stocking, when the hooks carried by the platen are conveyed externally to engage and withhold the loops formed by the needles of the cylinder; or a lowering is required when the thread pinching device, carried by the platen, must hook a new thread for the changing of the thread-holder.
A raising of the platen is furthermore required every time it is necessary to inspect the interior of the needlebearing cylinder wherein the descent of the stocking occurs during the formation thereof.
Such known kinds of machines, though they obtain the lowering of the platen according to the procesing requirements, have some disadvantages.
The most important of these disadvantages are related to the lever system which connects the cam-bearing cylinder, which controls the various processing phases, to the platen. The presence of these levers, in fact, constitutes a significant bulk, which contributes towards increasing the overall dimensions of the machine and hinders maintenance interventions in the areas proximate thereto.
Another disadvantage is due to the fact that these levers require accurate calibration during the setup of the machine, as well as periodic servicing to recover the play which unavoidably occurs due to machine wear.